Transmission of Cry1Ac from transgenic Bt cotton to the predatory ladybug Propylaea japonica via the whitefly Bemisia tabaci
Author of the article:ZHOU Fu-Cai** GU Ai-Xiang YANG Yi-Zhong*** SU Hong-HuaHU Qi-Jing YANG Ai-Min
Author's Workplace：School of Horticulture and Plant Protection College of Yangzhou University, Yangzhou 225009, China
Key Words：Bt transgenic cotton, Bemisia tabaci, Propylaea japonica, Cry1Ac, transmission
Abstract：[Objectives] The whitefly, Bemisia tabaci, is an economically important, non-target pest of Bt transgenic cotton. In this study, we examined the transmission of Cry1Ac from transgenic Bt cotton to the predatory ladybug, Propylaea japonica, (a natural enemy of the whitefly) in an effort to better evaluate the ecological safety of transgenic Bt cotton. [Methods] We used an enzyme linked immunosorbent assay (ELISA) to compare Cry1Ac levels in B. tabaci fed on the leaves of the conventional cotton cultivars SM3, SM33, and SY321 to those fed on the Bt transgenic cotton lines GK12, XM33B, and SGK321. [Results] Cry1Ac was detected in the adults, nymphs and honeydew of B. tabaci fed on Bt transgenic cotton. Cry1Ac was also detected in P. japonica that fed on these B. tabaci after just one day of feeding on B. tabaci nymphs that had consumed Bt transgenic cotton. The Cry1Ac content of P. japonica increased with increased with the duration of feeding, then stabilized after 6 to 8 days. The Cry1Ac content of P. japonica differed depending on the transgenic cotton line on which B. tabaci had fed. Although the Cry1Ac content of P. japonica declined when these were no longer exposed to food containing Cry1Ac, it did not disappear completely. The results of this study suggest that Cry1Ac from Bt transgenic cotton can be transferred to P. japonica through B. tabaci, and that B. tabaci can accumulate Cry1Ac. Cry1Ac levels in P. japonica eventually plateau; the speed of Cry1Ac accumulation in P. japonica, but not its saturation capacity, is related to the Cry1Ac content of their food. [Conclusion] Cry1Ac from Bt transgenic cotton can be transferred to P. japonica through B. tabaci, and B. tabaci can accumulate Cry1Ac. Cry1Ac levels in P. japonica plateau after 6 to 8 days; the speed of Cry1Ac accumulation in P. japonica, but not its saturation capacity, is related to the Cry1Ac content of their food.